pWRG/HTN-M(co)/pWRG/PUUV-M(United States Army Medical Research and Materiel Command)

In this paper, cement based on fused silica powder @ polyurethane urea (FSP@PUU) with a micro constrained damping structure was studied. Firstly, FSP@PUU core-shell particles were prepared by heterogeneous stepwise addition polymerization method and added into cement paste as damping filler to form a micro-constrained damping structure inside cement paste. The mechanical property and damping performance of cement-based composites were characterized by compressive strength, dynamic mechanical analysis (DMA) test and modal vibration test. The results showed that the damping performance of FSP @ PUU cement-based composites was affected by temperature, and the loss tangent of cement with 6wt% FSP@PUU increased to about 0.057 at -35 °C to 35 °C, which was 1.5 times cement paste within the glass transition temperature. With 6 wt% FSP@PUU, the damping ratio of cement-based composites increased by 58% compared with cement paste in the frequency range of 175-300 Hz, while the compressive strength decreased by only 5%. The cement with suitable FSP@PUU possesses excellent damping performance.

There is a need to create next-generation polymer composites having high property, unique function, and intelligent behaviors, such as shape memory effect (SME) and self-healing (SH) capability. Rare earth complexes can provide luminescence for polymers, and their dispersion is highly affected by ligand structures. Here, we created three different REOCs with different ligands before studying the effects of ligands on REOC dispersion in polyurea-urethane (PUU) with disulfide bonds in main chains. In addition, the effects of different REOCs on mechanical properties, luminescent functions, and intelligent behaviors of PUU composites were studied. The results showed that REOC I (Sm(TTA)₃phen: TTA, thenoyltrifluoroacetone; phen, 1,10-phenanthroline) has incompatible ligands with the PUU matrix. REOC I and REOC III (Sm(BUBA)₃phen: BUBA, 4-benzylurea-benzoic acid) with amine and urea groups facilitate their dispersion. It was REOC III that helped the maintenance of mechanical properties of PUU composites due to the good dispersion and the needle-like morphologies. Due to more organic ligands of REOC III, the fluorescence intensity of composite materials is reduced. The shape recovery ratio of the composite was not as good as that of pure PUU when a large amount of fillers was added. Besides, REOC I reduced the self-healing efficiency of PUU composites due to poor dispersion, and the other two REOCs increased the self-healing efficiency. The results showed that ligands in REOCs are important for their dispersion in the PUU matrix. The poor dispersion of REOC I is unbeneficial for mechanical properties and intelligent behavior. The high miscibility of REOC II (Sm(PABA)₃phen: PABA, 4-aminobenzoic acid) decreases mechanical properties as well but ensures the good shape recovery ratio and self-healing efficiency. The mediate miscibility and needle-like morphology of REOC III are good for mechanical properties. The shape recovery ratio, however, was decreased.